1. Field of the Invention
The present invention relates to a skin cosmetic composition having excellent utility, which gives sufficient moisturizing effects while being free from tackiness and having refreshing feeling. More specifically, the present invention relates to a skin cosmetic composition which can be used as lotion and the like.
The present invention also relates to a hydrogel particle and a process for preparing the same. More specifically, the present invention relates to a hydrogel particle in which an oil component is dispersed and which can be applied to cosmetics, pharmaceuticals, quasi-drug, foods and the like.
2. Discussion of the Related Art
Conventionally, as an aqueous cosmetic composition containing an oil component for the purposes of giving moisturizing effect, there have been known aqueous cosmetic compositions having an emulsion form, a solubilized form or a double-layer form.
The aqueous cosmetic composition having an emulsion form (milky lotion) can supplement an oily component to skin. However, the emulsion sometimes becomes unstable when a component which affects emulsion stability, such as an electrolyte is added to the composition. As a result, there are some defects such that moisturizing effects are impaired.
The aqueous cosmetic composition having a solubilized form (lotion) imparts moisturizing effects to skin to some extent. However, there are some defects in the composition such that the amount of an oil to be used in the composition should be relatively reduced, so that sufficient moisturizing effects are not maintained.
Also, the aqueous cosmetic composition having a double-layer form comprising an aqueous phase and an oil phase separated from each other is excellent in moisturizing effects, and their effects can be maintained. However, there are some defects in the composition such that the selection of their components used in the oil phase and the aqueous phase and the control of their compositional ratio would be difficult for giving a homogeneous dispersion only by shaking the composition upon use, and for recovering the original double layer by allowing it to stand. Especially, since a liquid oil is used in the composition in a large amount as a component for the oil phase, there are some defects in the composition such that the user's feel is unpleasant, and that the composition is applied inhomogeneously upon use, so that the composition is not good in fitness for the skin.
Under the above circumstances, there have been proposed various capsule-containing cosmetic compositions having both moisturizing effects and its maintaining effects, while exhibiting the characteristics of the aqueous cosmetic composition having a solubilized form (lotion).
For instance, there have been proposed a cosmetic composition containing an oil-in-water type (hereinafter referred to as O/W type) emulsion-incorporating capsule, wherein the capsule has a shell containing calcium alginate, the content of which is 0.1 to 1.0% by weight based on the entire amount of the capsule (Japanese Patent Laid-Open No. Hei 2-117610); an alginate capsule-containing cosmetic composition in which a part of the alginates is existing in the form of a polyvalent metal salt containing a barium salt as an essential component, wherein the capsules exist in the outer phase comprising an aqueous solution of carboxyvinyl polymer, the pH of which is adjusted (Japanese Patent Laid-Open No. Hei 11-29433); and a water-containing cosmetic composition comprising soft capsules or spheres, the substrate of which is agar (Japanese Patent Laid-Open No. Hei 1-193216).
The alginate-based capsule is prepared by reacting a water-soluble alginate with a water-soluble calcium salt to form a water-insoluble calcium alginate. Therefore, the incorporation of a surfactant, a water-soluble polymer, or an inorganic salt, those containing a di- or more valent metal ion, into the capsule is restricted. The stability of the alginate capsule depends upon pH, and the capsule is stable in a specified acidic region. However, the capsule is dissolved and broken in an alkaline region. In addition, if the washing of the polyvalent metal ions used in the curing reaction is insufficient after the preparation of the capsule, in the case where the outer phase comprises an aqueous medium containing a thickener not having enough tolerance against a salt, the viscosity of the aqueous medium is reduced by the remaining polyvalent metal ions, so that the dispersion of the capsule becomes inhomogeneous, thereby making it unfavorable in properties and appearance. Therefore, the aqueous medium is limited to those containing a thickener such as a polysaccharide which would not affect the aqueous medium, so that refreshing user's feel free from tackiness is difficult to be obtained.
The soft capsule, the substrate of which is agar necessitates agar in a high concentration in order to form a shell. Therefore, there are some defects such that some residue of agar remains on skin when the soft capsule is applied to the skin, causing unpleasant feeling. In addition, as a process for preparing a soft capsule, there has been known a process disclosed in Japanese Patent Laid-Open No. Hei 1-193216 mentioned above. However, it is difficult to obtain particles having high monodispersibility efficiently.
An object of the present invention is to provide a skin cosmetic composition in which particles are dispersed or suspended in a liquid medium, showing good appearance, being excellent in storage stability without allowing the particles to float or precipitate in the liquid medium with the passage of time, being smooth on skin when applied thereto, and having no residue of particles on the skin, thereby favorably exhibiting effects based on the ingredients.
Another object of the present invention is to provide a skin cosmetic composition in which specified particles are dispersed or suspended in a flowable substrate having a relatively low viscosity, and the visible particles give pretty impression, and the ingredients can be uniformly spread over the skin when the cosmetic composition is applied thereto, thereby realizing refreshing feel without tackiness.
A still another object of the present invention is to provide a hydrogel particle and a process for efficiently preparing the same, whereby the hydrogel particle having high sphericity and excellent monodispersibility, having an oil component therein stably dispersed in high content, being applied to cosmetics, pharmaceuticals, quasi-drug, and foods.
These and other objects of the present invention will be apparent from the following description.